For the Millers, their nine-game unbeaten run at the AESSEAL New York Stadium was ended in miserable fashion and just one win in 16 games leaves them looking over their shoulder, with Ryan Manning missing a late penalty.

The Baggies enjoyed the perfect start as they went ahead in just the sixth minute.

Clark Robertson was adjudged to have fouled Gayle 20 yards out and the striker stepped up to send the resulting free-kick under the wall and into the bottom corner for his 11th goal of the season.

Rotherham produced a spirited response and came close to equalising four minutes later when a corner was cleared to Manning and he cut inside and sent a thundering effort into the post, with Semi Ajayi's shot from the rebound then cleared off the line by Craig Dawson.

Not getting themselves level proved costly as West Brom doubled the lead in the 20th minute with consummate ease.

Barnes ghosted through a gaping hole in the home defence, slipped in Jay Rodriguez, whose shot hit the post, but Leicester loanee Barnes did what Ajayi could not and fire home the rebound.

Albion made it an opening 45 minutes to remember on the stroke of half-time as they extended their lead further.

Matt Phillips whipped in a free-kick from the left and Gayle got in front of his marker and poked home.

Gayle completed his treble nine minutes after the restart, but he had Millers goalkeeper Marek Rodak to thank for a terrible gaffe.

Trying to prevent a corner, Rodak scrambled to his left but inexcusably dropped the ball, allowing Gayle to snatch an early Christmas present by tapping into an empty net.

The Millers tried to restore some pride and Michael Smith forced keeper Sam Johnstone into a brilliant save to keep out a header and then Robertson saw another effort cleared off the line.

They had no better chance than the 76th-minute penalty, awarded after a foul by Tosin Adarabioyo on Richie Towell, but Manning hit the post and West Brom cleared.

Barnes and Hal Robson-Kanu went close to making it a record defeat at the New York Stadium for Rotherham, but they had to settle for four.

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